<pre>  /**
   * The constants used in this Content Widget.
   */
  public static interface CwConstants extends Constants {
    String cwFrameDescription();

    String cwFrameName();

    String cwFrameSetLocation();
  }

  /**
   * An instance of the constants.
   */
  private final CwConstants constants;

  /**
   * Initialize this example.
   */
  @Override
  public Widget onInitialize() {
    // Create a new frame
    String url = GWT.getModuleBaseURL();
    final Frame frame = new Frame(url);
    frame.setSize("700px", "300px");
    frame.ensureDebugId("cwFrame");

    // Create a form to set the location of the frame
    final TextBox locationBox = new TextBox();
    locationBox.setText(url);
    Button setLocationButton = new Button(constants.cwFrameSetLocation());
    HorizontalPanel optionsPanel = new HorizontalPanel();
    optionsPanel.setSpacing(8);
    optionsPanel.add(locationBox);
    optionsPanel.add(setLocationButton);

    // Change the location when the user clicks the button
    setLocationButton.addClickHandler(new ClickHandler() {
      public void onClick(ClickEvent event) {
        frame.setUrl(locationBox.getText());
      }
    });

    // Change the location when the user presses enter
    locationBox.addKeyDownHandler(new KeyDownHandler() {
      public void onKeyDown(KeyDownEvent event) {
        if (event.getNativeKeyCode() == KeyCodes.KEY_ENTER) {
          frame.setUrl(locationBox.getText());
        }
      }

    });

    // Add everything to a panel and return it
    VerticalPanel vPanel = new VerticalPanel();
    vPanel.add(optionsPanel);
    vPanel.add(frame);
    return vPanel;
  }

</pre>